Leveler assemblies, sometimes referred to as dock levelers, have had widespread use in the past to facilitate the loading and unloading of various parked vehicles--such as trucks, vans and the like. With the advent of fork lift trucks and palletized products, the bulk handling of such products within a plant or warehouse was greatly improved while at the same time providing better protection for the products as well as the person handling the products. To provide greater ease in handling such products on a loading dock, fork lift trucks are frequently required to move directly into and out of the storage compartment of the vehicle. Thus, in order to permit such an operation, the dock leveler compensates for any height variation which might exist between the dock loading platform and the bed of the vehicle.
Movement of the deck member, which comprises a component of the leveler assembly, was normally achieved by either mechanical means embodying various springs and counterweights, or by fluid pressure. It is with respect to leveler assemblies utilizing fluid pressure that the instant invention is particularly directed.
Heretofore in prior dock levelers of the fluid pressure type, the structural designs thereof were frequently beset with one or more of the following shortcomings: (a) they were of complex, costly construction susceptible to frequent malfunction; (b) they did not possess adequate safety and fail-safe features for the protection of personnel, the product and the equipment handling the product; (c) they were incapable of compensating for a wide range of height variations between the dock loading platform and the load-bearing bed of the vehicle; and (d) they required an inordinate amount of manual labor and/or fluid pressure to properly position the deck member relative to the vehicle bed.